new rear o2 sensor with non-fouler not working p0420

9

915_P5

:
02 Mazda P5
car had obx headers without non-fouler, so added the mod cleared the cel. 3-4 years later the cel came on with a p0421 bad rear o2 sensor, ordered new sensor and replaced it and now getting a p0420 bad cat. tried resetting ecu ran the car for miles and cel p0420 still pops up, what can I do or did do something wrong.
 
Ok guys I warrantied the o2 sensor, installed it yesterday night and just now the cel came on. What do you think it could be, I did notice hair line cracks on the header. I'll try to post up a pic, could this be causing the cel to turn on.
 
I had to stack 3 of those non foulers before the code would go away. And that's too bad about the cracks, but I don't they'd effect anything. At this point they are just barely leaking. I'd go get them welded asap though.
 
Forgot about that, I've deloomed most of my harness. My o2 sensor wires actually go behind the tranny and all the way underneath to make it cleaner. Is it attached to the 1st o2 sensor? Might be able to seperate the two and route it differently.

Sent from my SM-G900T using Tapatalk
 
Those cracks will leak into the cabin and could be dangerous. I had a Honda with one hair line crack and it was bad for me. I almost passed out a couple times thinking I was just sleep deprived but once I took off the heat shield I found it.
Is there anything else wrong with the header or cat? Take the header off and see if there are more cracks that could be a problem. If you let your car cool down and start it you can run your hand along and feel if there is anymore cracks/ air pressure. How long did you let it sit with battery disconnected?
 
Disconnected the battery last night for about 15-20 min, ill see how it does today. Forgot to do that when i changed it a couple days ago.
 
I have 2 non-foulers stacked with the one closest to header drilled out for o2 sensor to pass thru. Harness was long enough and have had no codes, ever, with 2 different headers. Have had header on this car since 2005 or 2006.
 
Just as I expected the light came on again just a few hours ago. I was how ever able get my state inspection yesterday after disconnecting the battery the night before, don't ask me how it passed cause it did. Why else could the light be coming on, does the brand have anything to do with it.
 
Shouldn't I had a cat delete and aftermarket header on without non foulers on my old honda and the light would switch on and off every day or every other day. So mazda is a little more sensitive.
 
That's what i was thinking, imma get the headers rewelded hopefully it'll fix the problem. Im running the same o2 on the mp3, stock exhaust and light went away. So maybe it is the cracks.
 
Hope I don't have cracks because mine just came on. I didn't have the cel as I just disconnected my battery like 2 days ago and haven't really driven it. I did the non-fouler and not like 5 miles or so did it come back on.
 
IMAG1523.jpg


Just did this yesterday and it threw out these codes P0140 & P0037. Is this something I fix with a new sensor with the non-fouler method. Silver linning, no cat code.
 
If your pre-cat craps out and you don't want to spend $1200 on a new one, the non-fouler will clear the code.

In California you must buy OEM.
 
Didn't even think of that. DUH, same thing we do when removing it and going with a header, lol.............
 
Please log in or register to reply here.

Similar threads

C
Another P0420 CEL
Replies
3
Views
2K
caldep105
C
BenjiHoggi
Protege5 won't idle after refueling (EVAP/O2 sensor issue?)
Replies
10
Views
2K
BenjiHoggi
BenjiHoggi
J
Non-fouler trick - both downstream sensors on CA emissions? 2007 Mazda3
Replies
2
Views
1K
negusm
N

Latest posts

Back